Full siblings (brother, sister): These siblings have the same father and mother.

Half siblings (half-brother, half-sister): These siblings have one parent that is the same. They either have the same father or the same mother.

Step siblings (stepbrother, stepsister): These sibling have different fathers and mothers but one of their parents is married to a parent of the other one.

example: John and Tom are step brothers because John's father is married to Tom's mother.

Siblings by breastfeeding: In Islam someone who is breastfed by a woman who is not their birth mother become siblings to the children of that woman if they are less than 2 years old and have been breastfed five times or more by that woman.